Running HOT!!! 78' engine No smog equip.

[F-junker]

Running 210 degrees, everything was fine until I replaced a manifold gasket to correct a vacuum leak.
The engine runs hot (up to 210ish) at high rpm down the road, slow down and she drops down to 190-200. This was never a problem before, new thermo (teq just tested out ok today), napa water pump-new, new auto meter temp guage and new sending unit for the old teq gauge as well- BOTH show hot temps.

Fan clutch was swapped for another unit, but doesn't seem to make a difference as thing gets hot driving down the road when a fan shouldn't make too much difference.

What is wrong that I know of... the carb

Carb does run a bit lean, I had Jim C look it over a bit and recommend an overhaul. This is going to happen soon. I did notice the venturies both have a number 1 on the body. The spare carb I have is a 79 and has both venturies marked 1 & 2. I swapped the jets from the primary and secondary to see if I had them backwards NO DICE. runs worse of course.

Could correcting the vac. leak and retuning the carb have leaned this engine out enough to run it this damn hot????? I thought the vac leak would have only made it run worse (leaner).

BTW- the radiator was cooked out recently and is in good order. Radiator cap fairly new and has no bind to it. This engine is a 79 with an oil cooler on it.
Carb is mid seventies and desmogged.

Any advice on this????

 

[Klunky Chris]

Ken,
Was chatting with dad on this.

We had an overheating issue with our 60 that turned out to be a very slow leak in the radiator. (pin-hole) The system couldn't get up to pressure and apparently couldn't cool itself properly.

Still doesn't fit your freeway only issue, but get a good pressure tester and presure test your system to make sure that isn't an issue.

 

[Fast Eddy]

I'll bet your radiator needs to be rodded out.

 

[ranger]

Already said the rad was "cooked out".

Check your timing.

 

[74fjsemistock]

Make that the Winter rig and get another for the topless season.

 

[Mace]

running lean and check timing..

 

[65swb45]

If you want to check for vacuum leaks, just spray check everything, put a guage on it, and look at the plugs. Obviously a lean condition will affect temps.

I am ALWAYS suspicious of fan clutches, and swapping one poor clutch for another poor clutch won't yield ANY reliable info. Bind up the clutch with something temporarily and see what happens. I'd bet money you'll see a difference.

Best

Mark A.

 

[highgravity]

I don't think it is fan clutch if the overheating is at highway temps. Sounds to me like you just need a new radiator, because it is getting maximum air flow at those speeds. Sometimes they can't be cleaned out and just need to be replaced. I had the exact same issue with a freshly reworked radiator. I upgraded to a 4 core, and have had 0 problems since.....well, except for that one time I forgot to top up after doing some engine work.

 

[F-junker]

Well the pressure test should be in order, I do agree on the timing issue as it can be a problem, however it's spot on for dui dizzy, gap adjusted accordingly. The man that did the radiator is very competant and rebuilds everything from John Deere to Ferrari, so I fairly comfortable with his work. A pin hole could have occured from many different things and should be investigate via pressure test. I will double check that timing today as well.

Anyone have any comment on the carb being set up with two identical venturies??? Seems kinda funny too me. I can't wait to send that thing off to Jim C. Your comments are appreciated, thanks Ken

 

[climber8483]

Did you "upgrade" to a high flow water pump? If so the water may not have enough time to cool in your radiator before entering your engine again. What is the outside temp? My cruiser will run at 210-215 on the highway going 60-70 in 95+ weather, but as soon as it cools down, she cools down. I was also reading/my buddy at NAPA told me that a 180 degree thermostat opens at 180 but is not truly fully open until closer to 200. Fan clutch is another thing, but if your not having any issues at lower speeds I can't see that as an issue.

Brittain

 

[fjwagon]

I agree, pressure test it and see if you loose pressure. I have had my radiators repaired in the past and found that after the second time it's best to buy a new one. It's not always a radiator problem , try checking hoses that could possibly be rubbing to metal surfaces to the point they start leaking. You can also remove the hoses going the thermstat housing and check if you have corrosion buildup at the neck. Just removing the crust off the neck of the thermostat housing may clear your problem. If you had overheating issues in the past your thermostat's integrety maby be shot. Inspect or replace the rad. cap. After it warms up check if the clutch is working by having someone click on the ignition while you watch the fan turn. I usually hold on to it with a couple of plastic spoons but I would not advise you do this. If the fan takes off then you have a good clutch if not you know what to do. Having a quart or two short will also give you heating problems. I pretty much listed all the problems I've had in the past.